The marketplace currently offers two primary types of drill chuck mechanisms for retaining drilling and driving tool bits. The traditional or “incremental” design typically consists of a mechanism that houses three adjustable jaws that protrude at an angle into a bore. An external sleeve is coupled to the jaws via internal gear teeth. When a tool is inserted into the bore, the sleeve is rotated by a user. As the sleeve is rotated in one direction, the jaws are forced towards the center of the bore to clamp a tool bit. When the sleeve is rotated in the opposite direction, the jaws are opened. This chuck style is able to accommodate a variety of tool sizes and shapes; however, changing a tool bit takes time.
It has long been recognized that the ability to quickly change tool bits in the spindle of a power tool is an advantageous feature. Construction workers and carpenters regularly change drill bits in numerous types of construction projects, often when the worker is in a position where it is difficult to change the bit, such as on a ladder. To change a drill bit, the carpenter must loosen the chuck, remove the old bit from the chuck, insert the new bit and tighten the chuck.
A second, more recent approach to chuck design allows for tools to be exchanged in a “quick-change” manner. Examples of quick-change mechanisms such as this are explained in U.S. Pat. Nos. 4,900,202 and 5,013,194, both of which are incorporated by reference herein. Quick-change chucks typically require the use of tools that have shafts or shanks that are of a consistent size (typically, a ¼″ hex shank), and usually have hexagonal cross sections. This style of chuck does not allow for accommodating a variety of tool shaft sizes.
The traditional three-jaw approach accommodates tools with round shafts and a range of different diameters and the more recent “quick-change” chucks allow for switching certain uniformly shaped and sized bits in a timely manner. However, there is still a need for a quickly and easily changeable tool holder to accommodate round shafts and shafts of various sizes.